Canadian Journal of Soil Science
0008-4271
1918-1841
Canada
Cơ quản chủ quản: Agricultural Institute of Canada , Canadian Science Publishing
Lĩnh vực:
Soil Science
Các bài báo tiêu biểu
Arbuscular mycorrhizae, glomalin, and soil aggregation Arbuscular mycorrhizae are important factors of soil quality through their effects on host plant physiology, soil ecological interactions, and their contributions to maintaining soil structure. The symbiosis is faced with numerous challenges in agroecosystems; in order to inform sustainable management strategies it is hence a high priority to work towards mechanistic understanding of arbuscular mycorrhizae contributions to soil quality. This review focuses on glomalin-related soil protein (GRSP), operationally defined soil C pools that have been linked to arbuscular mycorrhizal fungi (AMF). In discussing this protein pool, we propose a new terminology used to describe fractions of soil proteins and glomalin. GRSP concentrations in soil are positively correlated with aggregate water stability. GRSP has relatively slow turnover in soil, contributing to lasting effects on aggregation. Controls on production of GRSP at the phenomenological and mechanistic level are evaluated. While there are significant gaps in our knowledge about GRSP and glomalin (particularly at the biochemical level), it is concluded that research on GRSP holds great promise for furthering our knowledge of soil structure and quality, for informing suitable management, and as a foundation for novel biotechnological applications in agriculture and beyond. Key words: Glomalin, GRSP, soil structure, land use, restoration, soil protein, sustainability, arbuscular mycorrhizae
Tập 84 Số 4 - Trang 355-363 - 2004
DYNAMICS OF SOIL MICROBIAL BIOMASS AND WATER-SOLUBLE ORGANIC C IN BRETON L AFTER 50 YEARS OF CROPPING TO TWO ROTATIONS Amounts and turnover rates of biomass and water-soluble organic C (WSOC) were measured at the Breton plots where records of long-term management of a Gray Luvisolic soil are available. Plots (control, manure, and NPKS) which had been cropped to either a wheat-fallow or a wheat-oats-barley-forage-forage rotation for 50 yr were sampled 13 times during 1981 and 1982. Biomass C and flush of microbial N were measured using the chloroform fumigation technique. Long-term crop yields were used to derive C supply to the plots. Regression analyses were used to relate seasonal fluctuations in environmental conditions to biomass and WSOC dynamics. Reinoculation with soil was unnecessary but Lysobacter sp. formed a greater proportion of isolates following incubation of fumigated soil than of unfumigated samples. Reinoculation with Lysobacter sp. is suggested to provide a more standardized biological assay. The 5-yr rotation contained 38% more N but 117% more microbial N than did the 2-yr rotation, and manured treatments contained twice as much microbial N as did NPKS or control plots. A management effect on soil organic matter quality is indicated. Averge turnover rates of biomass were 0.2–3.9 yr−1 ; being 1.5–2 times faster in the 2-yr rotation than in the 5-yr rotation. Replenishment of the WSOC component would have to occur 26–39 times yr−1 to supply microbial turnover. Most of the biomass must be dormant because annual C inputs are two orders of magnitude less than maintenance energy requirements. Seasonal variations in biomass were most consistently related to losses during desiccation and regrowth upon moistening. Regrowth appears to be at the expense of native soil organic matter. Management practices and environmental conditions therefore affect amount of organic matter by controlling both input of C and biomass turnover. Key words: Crop rotations, Luvisol, organic matter, biomass, soluble C, Breton plots
Tập 66 Số 1 - Trang 1-19 - 1986
The role of organic amendments in soil reclamation: A review Larney, F. J. and Angers, D. A. 2012. The role of organic amendments in soil reclamation: A review. Can. J. Soil Sci. 92: 19–38. A basic tenet of sustainable soil management is that current human activities are not detrimental to future generations. Soils are degraded by natural events (erosion) or industrial activity. A prevalent feature of degraded or disturbed soils is lack of organic matter compared with adjacent undisturbed areas. Organic amendments, such as livestock manure, biosolids, pulp and paper mill by-products, wood residuals and crop residues, are produced in abundance in Canada and could be widely used in soil reclamation. Biosolids production is ∼0.5 Tg yr−1 (dry wt.); paper mill sludge generated in the province of Quebec was ∼2 Tg (wet wt.) in 2002. This review paper examines mechanisms through which organic amendments affect soil properties (physical, chemical, biological) and describes the role of organic amendments in reclamation, with emphasis on amendment types and application rates for soil amelioration and biomass production. Single large applications of organic amendments can accelerate initial reclamation and lead to self-sustaining net primary productivity. Readily decomposable organic amendments may provide immediate, but transient, effects, whereas stable, less decomposable materials may provide longer-lasting effects. Using organic amendments for reclamation is mutually beneficial wherein waste products from agriculture, forestry and urban areas help other sectors meet their land reclamation goals.
Tập 92 Số 1 - Trang 19-38 - 2012
Changes in soil carbon under long-term maize in monoculture and legume-based rotation Legume-based cropping systems could help to increase crop productivity and soil organic matter levels, thereby enhancing soil quality, as well as having the additional benefit of sequestering atmospheric C. To evaluate the effects of 35 yr of maize monoculture and legume-based cropping on soil C levels and residue retention, we measured organic C and 13 C natural abundance in soils under: fertilized and unfertilized maize (Zea mays L.), both in monoculture and legume-based [maize-oat (Avena sativa L.)-alfalfa (Medicago sativa L.)-alfalfa] rotations; fertilized and unfertilized systems of continuous grass (Poa pratensis L.); and under forest. Solid state 13 C nuclear magnetic resonance (NMR) was used to chemically characterize the organic matter in plant residues and soils. Soils (70-cm depth) under maize cropping had about 30-40% less C, and those under continuous grass had about 16% less C, than those under adjacent forest. Qualitative differences in crop residues were important in these systems, because quantitative differences in net primary productivity and C inputs in the different agroecosystems did not account for observed differences in total soil C. Cropping sequence (i.e., rotation or monoculture) had a greater effect on soil C levels than application of fertilizer. The difference in soil C levels between rotation and monoculture maize systems was about 20 Mg C ha-1 . The effects of fertilization on soil C were small (~6 Mg C ha-1 ), and differences were observed only in the monoculture system. The NMR results suggest that the chemical composition of organic matter was little affected by the nature of crop residues returned to the soil. The total quantity of maize-derived soil C was different in each system, because the quantity of maize residue returned to the soil was different; hence the maize-derived soil C ranged from 23 Mg ha-1 in the fertilized and 14 Mg ha-1 in the unfertilized monoculture soils (i.e., after 35 maize crops) to 6-7 Mg ha-1 in both the fertilized and unfertilized legume-based rotation soils (i.e., after eight maize crops). The proportion of maize residue C returned to the soil and retained as soil organic C (i.e., Mg maize-derived soil C/Mg maize residue) was about 14% for all maize cropping systems. The quantity of C3-C below the plow layer in legume-based rotation was 40% greater than that in monoculture and about the same as that under either continuous grass or forest. The soil organic matter below the plow layer in soil under the legume-based rotation appeared to be in a more biologically resistant form (i.e., higher aromatic C content) compared with that under monoculture. The retention of maize residue C as soil organic matter was four to five times greater below the plow layer than that within the plow layer. We conclude that residue quality plays a key role in increasing the retention of soil C in agroecosystems and that soils under legume-based rotation tend to be more “preservative” of residue C inputs, particularly from root inputs, than soils under monoculture. Key words: Soil carbon, 13 C natural abundance, 13 C nuclear magnetic resonance, maize cropping, legumes, root carbon
Tập 81 Số 1 - Trang 21-31 - 2001
EFFECTS OF INITIAL CHEMICAL COMPOSITION ON DECOMPOSITION OF ROOTS OF THREE GRASS SPECIES Grass root production is a major source of C entering Chernozemic soils. The influence of the initial chemical composition of the roots of three grass species on decomposition was studied in a laboratory incubation experiment. Roots of Stipa comata Trin. and Rupr., Stipa spartea Trin. var. curtiseta Hitchc., and Festuca scabrella Torr. were incubated at 28 C for 47 wk. Carbon dioxide production and percent loss of carbohydrate were inversely related to [(C:N) (% lignin)] (% carbohydrate−½ ). Percent loss of lignin, however, was directly proportional to this factor. This relationship was also found to fit data in the earlier literature. Decomposition rate appeared to be slower in the laboratory in the absence of soil than has been reported for decomposition rates in field soils. The data are discussed with reference to the dynamics of plant residues and organic matter in soil systems. It is postulated that the effect of soil in controlling decomposition may be as great as the effect of the substrate.
Tập 57 Số 2 - Trang 205-215 - 1977
Towards accurate measurements of soil organic carbon stock change in agroecosystems In response to Kyoto Protocol commitments, countries can elect agricultural carbon sinks to offset emissions from other sectors, but they need to verify soil organic carbon (SOC) stock change. We summarize issues we see as barriers to obtaining accurate measures of SOC change, including: soil depth, bulk density and equivalent soil mass, representation of landscape components, experimental design, and the equilibrium status of the SOC. If the entire plow depth is not considered, rates of SOC storage under conservation compared with conventional tillage can be overstated. Bulk density must be measured to report SOC stock on an area basis. More critical still is the need to report SOC stock on an equivalent mass basis to normalize the effects of management on bulk density. Most experiments comparing SOC under differing management have been conducted in small, flat research plots. Although results obtained from these long-term experiments have been useful to develop and validate SOC prediction models, they do not adequately consider landscape effects. Traditional agronomic experimental designs can be inefficient for assessing small changes in SOC stock within large spatial variability. Sampling designs are suggested to improve statistical power and sensitivity in detecting changes in SOC stocks over short time periods. Key words: Soil organic carbon change, agroecosystems, experimental design, sampling depth
Tập 86 Số 3 - Trang 465-471 - 2006
DISTRIBUTION AND MOBILITY OF PHOSPHORUS IN GRASSLAND AND FOREST SOILS OF SASKATCHEWAN Soil phosphorus transformations and losses were measured in three profiles representative of an environmental gradient covering a grassland to forest transition: a Calcareous Brown, an Orthic Black and an Orthic Gray Luvisol. A sequential extraction procedure was used to measure the different forms of both inorganic (Pi ) and organic (Po ) phosphorus present in soil horizons. The mobilities of phosphate anions and of some selected (Po ) compounds (glucose 6-phosphate, choline phosphate and adenosine triphosphate) were estimated through isotopic dilution kinetic experiments, and indicated that all the tested Po compounds had a higher mobility than phosphate anions in B horizons; also, Po was predominant over Pi in the water extracts from these soils. A mass-balance approach (Pedogenic Index) which incorporates depth-bulk density parameters in measuring the composition of soil horizons was used to calculate losses of Pt and apatite-P (HCl-Pi ). Both grassland soils behaved similarly; they lost 500–550 kg P ha−1 (20%) of their original Pt and 30% of the initial HCl-Pi fraction was either transformed to various other forms of P or lost from the solum. Losses of Pt (3020 kg P ha−1 : 41 %)and of HCl-Pi (70%) were much higher in the Gray Luvisol. Since losses of Pt could not be due to leaching of phosphate anions through the profile, the importance of Po in P leaching should be considered along with surface runoff in determining the fate of P in these soils. Key words: Pedogenic index, P mass balance, P fractionation, organic P leaching, P mobility
Tập 69 Số 2 - Trang 401-416 - 1989
N<sub>2</sub>O fluxes in soils of contrasting textures fertilized with liquid and solid dairy cattle manures Manure is known to increase soil N2 O emissions by stimulating nitrification and denitrification processes. Our objective was to compare soil-surface N2 O emissions following the application of liquid and solid dairy cattle manures to a loamy and a clay soil cropped to silage maize. Manures were applied in 2 consecutive years at rates equivalent to 150 kg total N ha-1 and compared with a control treatment receiving an equivalent rate of synthetic N. Soil-surface N2 O fluxes, soil temperature, and soil water, nitrate and ammonium contents were monitored weekly in manured and control plots. From 60 to 90% of seasonal N2 O emissions occurred during the first 40 d following manure and synthetic fertilizer applications, indicating that outside that period one or several factors limited N2 O emissions. The period of higher emissions following manure and fertilizer application corresponded with the period when soil mineral N contents were highest (up to 17 g NO3 − -N m-2 ) and water-filled pore space (WFPS) was greater than 0.5 m3 m-3 . The absence of significant N2 O fluxes later in the growing season despite high WFPS levels indicated that the stimulating effect of organic and synthetic N additions on soil N2 O production was relatively short-lived. Fertilization of silage maize with dairy cattle manure resulted in greater or equal N2 O emissions than with synthetic N. This was observed despite lower overall soil mineral N contents in the manured plots, indicating that other factors affected by manure, possibly additional C substrates and enhanced soil respiration, resulted in greater denitrification and N2 O production. Silage maize yields in the manured soils were lower than those receiving synthetic N, indicating that the N2 O emissions per kilogram of harvested biomass were greater for manures than for synthetic N. Our results also suggest that the main source of N2 O was nitrification in the loam and denitrification in the clay soil. There was no clear difference in N2 O emissions between liquid and solid manures. The variable effects of liquid and solid manure addition reported in the literature on soil N2 O emissions likely result from the variable composition of the manures themselves as well as from interactions with other factors such as soil environment and farming practices. A better characterization of the availability of manure C and N is required to assess the impact of manure application on soil N2 O emissions under field conditions. Key words: Greenhouse gases, N2 O, maize, manure
Tập 88 Số 2 - Trang 175-187 - 2008
Root mass distribution under conventional and conservation tillage Tillage effects on the soil environment suggest that it may influence rooting depth and root distribution. In this study, corn (Zea mays L.) rooting depth and root mass distribution were compared under conventional and conservation (chisel, ridge, no-) tillage on sandy loam and clay loam soils at Ottawa, Ontario. Root depth and distribution in 0.10-m vertical increments during vegetative growth were estimated using a combination of excavation of the surface horizon (0–0.10 m) and 0.05-m diameter cores obtained in the row and midway between two rows over a 3-yr period. An exponential model was used to fit root mass distribution data normalized with respect to total root density summed over all increments and maximum rooting depth in the profile. Soil moisture, temperature, mechanical resistance and bulk density varied with tillage treatment, but differences were not associated with root mass distribution. Rooting depth varied with soil texture, year and tillage, with increased rooting depth associated with increased tillage and decreased moisture in surface soil layers. In contrast, a common exponential model was found to fit normalized root mass distribution data under all tillage treatments. Our data suggest that simulation of root mass distribution under all tillage practices is possible if rooting depth and root mass density of the surface soil layer are known. Key words: Corn, model fitting, root distribution, tillage, Zea mays
Tập 76 Số 1 - Trang 23-28 - 1996
Nitrogen release during decomposition of crop residues under conventional and zero tillage The litter-bag method was used in field experiments to determine nitrogen (N) loss patterns from decomposing red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues under conventional and zero tillage. Nitrogen contained in crop residues ranged from 10 kg ha-1 in wheat under both tillage systems to 115 kg ha-1 in clover GM under zero tillage. The patterns of N loss (i.e., release), particularly from GM residues, over 52-wk periods varied with tillage, i.e., residues lost N more rapidly under conventional tillage than under zero tillage in the first 5 to 10 wk after residue placement. Net N immobilization was sometimes observed, particularly under zero tillage. Where net N release occurred, it ranged from 22% of wheat N under conventional tillage to 71% for clover N under conventional tillage; it was positively correlated with residue N concentration and microbial activity, and negatively correlated with C:N and lignin:N ratios in one study period. The amounts of N released were 2 kg ha-1 from wheat, 10 to 25 kg ha-1 from canola, 4 to 18 kg ha-1 from pea, and 46 to 69 kg ha-1 from GM residues. Therefore, when grain is harvested, the remaining crop residues do not release much N to the soil in the first year of decomposition, but the N stored in soil is presumably released in subsequent years. Key words: Crop residues, crop rotation, N mineralization, organic soil amendments
Tập 86 Số 1 - Trang 11-19 - 2006